Subject: '97 Dodge Dakota Oil Pressure Drop when Warm
Date: Wednesday, December 06, 2006 12:30 PM
'97 Dodge Dakota 4x4 5.2L
I have been chasing this oil pressure problem around and decided to see what
this group thinks. The OP is 40+ when started and remains until normal
operating temperature is achieved. It then drops down to ~20psi or the low
range on the gauge, but not below the lower limit indicator. When under
acceleration or load it sounds like lifter rattle. I replaced the sending
unit because the old one wouldn't read the low signal and dropped the gauge
to 0psi. New filter and oil (20W-50 Florida) and still not maintaining the
pressure when normal operating temp. I read a post on a web site that
explained the 'Thrust Bearing' was bad which allowed a 1/8" shift in the
crank position and after replacing the thrust bearing (and I would expect
the rest of the mains) the oil pressure drop when warm disappeared. I would
think that if the thrust bearing was bad that it would have the pressure
problem even when the engine was cold or just warming up. I can drive it 45,
55, and the pressure still remains at 40+ until it reaches N.O.T. and then
drops to the lower range of the gauge (~20psi?). That makes me think along
the lines of a viscosity problem or a pump that has worn impellers. IE. the
oil remains thick enough for the pump to work at lower temperatures but as
soon as the oil is hot and the viscosity drops the problem surfaces. Any
comments on your experiences with fixing this problem would be appreciated.
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That oil pressure drop sounds normal to me. If it were mine I'd put 10W-30
back in it and check the pressure again. If I still had 20 psi at idle hot
I'd be happy. The "lifter rattle" noise may be caused by the spark plug wire
routing. Try this:
OK. After I reinstalled the plug wires with the proper convolute and routing
98% of the knock is gone. I had previously rerouted the wires per All Data,
but I didn't have the convolute at the time. The previous owner had the
wires routed all wrong. Hopefully there wasn't much engine damage from
premature crossfire. The oil pressure goes to the lower end of the range,
but within the operating range. One more thing, would you recommend running
an engine flush (kerosene) through to clean out the sludge? The 5.9L has
100,000 on it now and there is a littler lifter noise at higher RPM's. I
bought the truck with 97,000 on it and when I changed the oil the first time
the gauge dropped to 0 psi and the check gauges light went on and wouldn't
work at idle until I replaced the oil sending unit.. It must have been a
coincidence that the oil pressure sensor was bad, but functioning until the
new filter put increased pressure on the oil sending unit. I have read in
several other forums that the Dodge Dakota has been known to have oil
pressure problems. However, it didn't really indicate which engines had the
problem. It seemed the 3.9L was mentioned more than the others. I have the
materials for the oil change, but wanted your opinion on the flush first.
Thanks for making me go back and finish the wire routing with convolute.
After many years working on engines, I couldn't believe the wire routing
would cause that much knock. It definately sounded like mechanical damage!
Thanks again Ken!
Cleaning out the sludge might cause some oil leaks. Sometimes when gaskets
get old and cracked, sludge creeps in there to fill the voids. When you
clean the sludge out the gaskets start leaking. I'd leave it alone.
My 98' Dakota was having about the same problem. Turned out to be the
brand new oil filter. Replaced it with a Wix filter and oil pressure
shot up to the upper mark. However I think the drop is normal after
the oil gets warm and engine comes to an idle, mine drops just below
40psi. I would not try the flush out the sluge, it may do more bad
Your post says 40 psi ?? First when it is cold you should get maybe 80 psi
oil pressure If you do not Verify it with a mechanical oil pressure gauge.
If low The only thing to do is CHECK THE BEARINGS. I ignored a oil
pressure loss on a LA360 pre magnum had 20 at idle not its normal 40 psi
ended up breaking the crank which I suspect was caused by the bad bearing
clearences allowing the crank to flex
My last truck was pretty high mileage. Castrol GX or GTX, or whatever
it was. That was the only brand that quieted the rod knock longer than
two or three days after an oil change. Please consider a different
brand of oil.
My favorite mechanic likes Quaker State, but I didn't have as good a
results as I did with Castrol. He'd had several experiences with
people having low oil pressure, after an oil change at a Valvoline
place. He'd drain the oil, put in Quaker State, and they'd be good to
Please try Castrol. Might be the answer.
Christopher A. Young
You can't shout down a troll.
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